Vector 3-component 3-dimensional Kirchhoff prestack migration

Abstract

An apparatus and a method for migration of three components, 3-Dimensions seismic (3-C, 3-D) data acquired by down-hole receivers and surface seismic sources. This method utilizes full 3 components reflection wave field. It uses a dynamic, vector energy mapping method to image a reflection position and maps each time sample only to its reflected image point. Therefore, this method reduces unwanted data smearing and false mirror images. This method overcomes the weakness of using only a single component trace or pre-rotated three-component traces in the 1-C or 3-C 3-D VSP migration and produces better 3-D image.

1. A system configured to evaluate an earth formation, the system comprising:
 a seismic source at least one source position configured to generate seismic waves into the earth formation, 
 at least one receiver configured to receive three components of seismic data at a plurality of receiver positions the at least one source position and the plurality of receiver positions defining a plurality of source-receiver combinations; and 
 a processor configured to:
 (i) use a vector combination of the three components of the seismic data to define a contribution from each of the plurality of source-receiver combinations to an amplitude of an image at a plurality of image points using traveltimes from the at least one source position to the plurality of image points and traveltimes from the plurality of image points to the plurality of receiver positions; 
 (ii) combine, at each of the plurality of image points, the contributions to the amplitude from each of the plurality of source-receiver combinations to produce an image of the earth formation. 
 
 
   
   
     2. The system of  claim 1  wherein the at least one source position is at least one of (i) a surface location, and (ii) a downhole location. 
   
   
     3. The system of  claim 1  wherein the three components of seismic data are substantially orthogonal to each other. 
   
   
     4. The system of  claim 1  wherein at least one of the plurality of image points is part of a reflecting interface. 
   
   
     5. The system of  claim 1  wherein the processor is further configured to use a velocity model for obtaining the traveltimes. 
   
   
     6. The system of  claim 1  wherein the seismic waves by the seismic source comprise at least one of: (i) compressional waves, and, (ii) shear waves. 
   
   
     7. The system of  claim 1  wherein a portion of the seismic data received by the at least one receiver corresponds to at least one of: (i) a compressional wave, and, (ii) a shear wave. 
   
   
     8. The system of  claim 1  wherein the processor is further configured to process the three components of seismic data by further rotating the three components of the received seismic data in a specified direction. 
   
   
     9. The system of  claim 8  wherein the specified direction is in a vertical plane passing through the at least one source position. 
   
   
     10. The system of  claim 8  wherein the specified direction is defined by a line joining at least one of the plurality of image points to at least one of the plurality of receiver positions. 
   
   
     11. The system of  claim 1  the processor is further configured to use the vector combination of the three components of seismic data by further rotating a vector sum of the three components of the seismic data in a specified direction. 
   
   
     12. The system of  claim 11  wherein the specified direction is in a vertical plane passing through the at least one source position and the at least one of the plurality of receiver positions. 
   
   
     13. The system of  claim 11  wherein the specified direction is defined by a line joining at least one of the plurality of image points to at least one of the plurality of receiver positions. 
   
   
     14. The system of  claim 1  wherein the plurality of image points are on a grid of output points. 
   
   
     15. The system of  claim 1  wherein the processor is configured to define the contribution by further applying a correction that is at least one of: (i) an amplitude correction, and, (ii) a phase correction. 
   
   
     16. The system of  claim 15  wherein the at least one source position further comprises a plurality of additional source positions. 
   
   
     17. The system of  claim 1  wherein the at least one source position further comprises a plurality of additional source positions.